1. Field of the Invention
The present invention relates to an image processing apparatus and an X-ray diagnostic apparatus. More particularly, it relates to a support technique used in image pickup in an X-ray diagnostic apparatus whereby an operator moves a device into a blood vessel in an intravascular interventional treatment.
2. Description of the Related Art
Recent advances in CT imaging technology have made it easier to obtain a three-dimensional (3D) image of a cardiac coronary artery. Accordingly, there is an idea of using a CT 3D image to improve an intravascular treatment.
In an intravascular operation, an X-ray diagnostic apparatus is used, and a treatment is administered with a real-time view of its projection fluoroscopy image. Devices such as a catheter and a guide wire (hereinafter referred to as a wire) are used in the treatment. After the wire has been inserted into a coronary artery, it reaches a lesion through several vascular bifurcations, passes through the lesion, moves to a peripheral part with a small vessel diameter, and is fixed there. Once the wire is fixed, for example, a stenotic dilatation is administered using a device such as a stent. Then, the whole treatment operation is finished, and when it is judged in a final contrast study that the treatment can be ended, the wire which was first inserted and fixed is pulled out.
When the wire is first inserted, it is important to move the wire so that blood vessel walls may not be damaged. This must be taken care of particularly in the following cases: For example, as shown in FIG. 1A, a catheter 6 is inserted through a main artery 2, a coronary artery 4, etc., and force is applied at a part with a small thickness of the vessel wall so that a wire 8 may not break through the vessel. Otherwise, as shown in FIG. 1B, attention should be paid so that the wire 8 may not pick and break a soft tissue 10 such as soft plaque.
However, the X-ray fluoroscopy image does not enable the visualization of the thickness of the vessel wall and the softness of the plaque. Thus, at present, the wire is moved by the intuition and experience of an operator.
On the other hand, a recently available CT image has enabled the visualization of the thickness of the vessel wall and the softness of the plaque. There are therefore needs of operators that the CT image be utilized to display a cross-sectional image of the current position of the distal end of the wire being moved by the operator. That is, there is a desire that a cross-sectional image of a CT image corresponding to the distal end position of the wire being moved by the operator be displayed.
In order to achieve this, the following three steps are required: (i) adjustments of an X-ray two-dimensional (2D) image and a CT 3D image, (ii) the determination of three-dimensional coordinates of the distal end of the wire, and (iii) the determination of the direction of a section. Among these steps, (i) concerns the technical field called 2D/3D registration for aligning the 2D image with the 3D image, as described in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-290192. There have also been proposed various methods in the field of image processing.
As to (ii), it is theoretically impossible to obtain coordinates on the 3D image if coordinates on the 2D image in one direction of the X-rays are only obtained. While there have been various ideas to solve this, methods carried out with image processing have their limitations. Moreover, as to (ii), even if coordinates on the 2D image are obtained at a certain moment, the operator moves the wire at the next moment, thus coordinates on the 2D image are different at the next moment.
Therefore, it has been difficult in the prior arts to specify the coordinates of the distal end of the wire on the 3D image. Thus, for example, a technique using a three-dimensional position sensor has been proposed. However, this is a special tool and is not preferable.
Furthermore, (iii) can be theoretically achieved in image processing, but is difficult. That is, the travel of a blood vessel is determined from an image, and an image in a direction perpendicular to this travel is generated. This requires accurate binarization and extraction of the blood vessel, processing of branch vessels and analysis of the main components, therefore perfect determination of the travel is difficult in terms of image processing.
As described above, even if the prior arts are combined together, it has been difficult to display a cross-sectional image of a CT image corresponding to the distal end position of the wire being moved by the operator.